Role of H1 receptor in inflammatory response during ventilator-induced lung injury in rats

Objective To evaluate the role of H1 receptor in inflammatory responses during ventilator-induced lung injury (VILI) in rats. Methods Thirty clean-grade healthy male Sprague-Dawley rats, aged 9-10 weeks, weighing 250-300 g, were divided into 3 groups (n=10 each) using a random number table method: control group (group C), VILI group (group V) and H1 receptor antagonist clemastine group (group Cle). The animals were anesthetized and tracheostomized, and the rats in group C kept spontaneous breathing.The rats were mechanically ventilated for 4 h with the tidal volume of 40 ml/kg, respiratory rate 40 breaths/min, inspiratory/expiratory ratio 1∶1, and inspired oxygen fraction ratio 21% in group V. In group Cle, clemastine 0.9 mg/kg was intramuscularly injected at 30 min before anesthesia, the animals were tracheostomized after being anesthetized, and then the rats were mechanically ventilated with the same ventilator settings as group V. The animals were sacrificed at 4 h of ventilation, bronchoalveolar lavage fluid (BALF) was collected for determination of concentrations of total protein, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and the lung specimens were obtained for microscopic examination of pathologic changes and for determination of wet/dry weight ratio (W/D ratio). Results Compared with group C, the concentrations of total protein, IL-6 and TNF-α in BALF and W/D ratio were significantly increased in group V (P<0.05). Compared with group V, the concentrations of total protein, IL-6 and TNF-α in BALF and W/D ratio were significantly decreased in group Cle (P<0.05). The pathologic changes of lung tissues were significantly attenuated in group Cle as compared with group V. Conclusion H1 receptor is involved in the process of inflammatory responses during VILI in rats. Key words: Receptors, histamine H1; Ventilator-induced lung injury; Inflammation